How to upgrade overnight / avoid system downtime

When a new version is released I’d like to review the blog and if I am happy it isn’t going to mess anything I want to have my Pi upgrade at a time when nothing is going to be impacted.
Can I schedule an upgrade ?

Taking this one or two steps further!! Is it possible to have two Pi’s running HA in a way to form a resilient system so that one is live and active and the other is in a stand-by mode until needed.? Eg to facilitate ugrades without down-time.